Approaches to Fabrication of Photochromic Aerogels

Aerogels are nanoporous materials that are comprised of 95 - 99% air. They have unique properties, such as being insulating materials, as well as having a high specific area and porosity. Silica aerogels can be used to make windows due to their translucent nature. In the aerogel lab at Union College, various projects have been conducted to characterize these properties and learn more about aerogels. One of these projects includes producing colored aerogels through the use of different colored dyes, which has been successful. These can then be used in producing windows with a stained glass effect. My work builds on those experiments by investigating the ability to produce aerogels that experience photochromic effects, which means the color of the aerogel would change based on exposure to different light intensities. This could be useful in a real-world application as no shades would be needed since the window would act as its own shade, darkening when the sunlight is over a certain intensity. Initial experiments focused on the use of photochromic dyes. Due to the high temperature and pressure required for processing that the aerogel must undergo, that approach has not been successful: the resulting materials were not translucent aerogels. Another approach under investigation is to use salts in an ion-exchange method to produce a photochromic effect. Using silver nitrate (AgNO3) in the precursor solution for the aerogel resulted in gels that showed no photochromic properties. The current approach is to synthesize silver chloride (AgCl) nanoparticles to use in the aerogel solution and characterize the results. This presentation will focus on the approaches and results taken to obtain photochromic aerogels.